In a particular type of an optical projection video display system, an actuated mirror array is used to control the light modulation for each pixel. In one system, the mirror array is illuminated by a source of optical energy. Under electronic control, the orientation of each of the mirrors in the array is varied to determine a propagation path for a beam of light reflecting from each mirror. An example of an optical projection video display system is shown in FIG. 1. In this system light is emitted from a light source 120, and is reflected off a Schtieren stop mirror 122 at an angle toward the actuated mirror array 124. The light is reflected from the actuated mirror array at a controlled angle. The angle is controlled through the actuation of the mirror array. The light reflected from the mirror array 124 passes through a second lens 126, bypasses the Schlieren stop mirror, and passes through a third lens 128 to a screen. The present invention discloses actuated mirrors for mirror arrays used in such an optical projection video display system.
A unimorph is a piezoelectric element externally bonded to a metal foil. The metal foil is controlled by applying a DC electrical signal across the piezoelectric material, which causes the piezoelectric material to change shape. The change in shape of the piezoelectric material causing an axial buckling or deflection in the metal foil as the foil opposes movement of the piezoelectric material. The degree of buckling of the metal foil is controlled by the amplitude of the DC electrical signal. A bimorph includes two layers of piezoelectric element. It is known in the art to create unimorph and bimorph piezoelectric elements by using adhesives to bond the metal foil to the piezoelectric elements. For example, U.S. Pat. No. 5,085,497 discloses methods for fabricating mirror arrays for optical projection systems.
A problem with the known actuated mirror arrays, however, is that the mirror arrays are difficult to manufacture. Another problem with the known actuated mirror arrays is that displacement of the mirrors is not as great as desired. For these reasons, an improved actuated mirror array is needed.